How did Alfred T. Mahan and George F. Kennan influence U.S. foreign policy? 

Mahan and Kennan

Truman Doctrine – 1947 ($400 million in aid) 

In 1947 President Truman asked for and received from the U.S. Congress $400 million to provide assistance “to support free peoples who are resisting attempted subjugation [enslavement] by armed minorities [communists] or by outside pressures.”  Providing military and economic assistance to nations resisting communist takeovers became known as the Truman Doctrine.  The first nations to receive aid under the Truman Doctrine were Greece and Turkey, both of which then successfully defeated attempted communist takeovers.

"The Marshall Plan was a spectacular success. American dollars pumped reviving blood into the 
economic veins of the anemic Western European nations."   American Pageant - Page 871

Marshall Plan -1947 ($17 billion in aid) 

In 1947 U.S. Secretary of State George Marshall created a plan to rebuild a Europe devastated by World War II.  All European nations, including the Soviet Union, could receive U.S. dollars to rebuild their devastated economies as long as the money was spent on products made in the United States.  In 1948 the U.S. Congress approved $17 billion in aid.  Nations receiving Marshall Plan aid were Great Britain, France, Portugal, Spain, Belgium, the Netherlands, Luxembourg, West Germany, Denmark, Norway, Sweden, Switzerland, Austria, Italy, Greece, and Turkey.